3.2.2/3.2.3 - Group 2 and Group 7 Flashcards
Define a reducing agent
An electron donor
Describe the trend in the reducing strength of halides
- Increases down the group
- Ionic radius increases
- Weaker attraction between outer electron and nucleus
What is the observation for SO2?
(Acidic) Choking gas
What is the observation for S?
Yellow solid
What is the observation for H2S
Smell of bad eggs
What forms SO2?
Br- and I-
What forms S?
I-
What forms H2S?
I-
What is the observation for this reaction:
2I- -> I2 + 2e-
Black solid
What is the observation for this reaction:
2Br- -> Br2 + 2e-
Brown fumes
What do F and Cl undergo when they react with H2SO4?
Acid-base reactions
What is the ionic equation for H2SO4 reaction with F and Cl?
H+ + F- -> HF
H+ + Cl- -> HCl
What is the observation for H2SO4 and F?
Misty fumes of HF gas
What is the observation for H2SO4 and Cl?
Misty fumes of HCl gas
What are the steps for the halide test?
- Dissolve sample in water
- Add HNO3
- Add AgNO3(aq) solution
What are the observations from adding HNO3 and AgNO3 in a halide test?
- Fluoride: No precipitate
- Chloride: White precipitate
- Bromide: Cream precipitate
- Iodide: Yellow precipitate
What are the observations after adding dilute NH3?
- Chloride: White precipitate dissolves
- Bromide: Cream precipitate insoluble
- Iodide: Yellow precipitate insoluble
What are the observations after adding concentrated NH3?
- Bromide: Cream precipitate dissolves
- Iodide: Yellow precipitate insoluble
Equation for AgCl and NH3
AgCl(s) + 2NH3 -> [Ag(NH3)2]+(aq) + Cl-(aq)
Equation for AgBr and NH3
AgBr(s) + 2NH3 -> [Ag(NH3)2]+(aq) + Br-(aq)
Define oxidising reagent
Electron acceptor
What is the trend in oxidising ability of halogens?
- Decrease down the group
- Larger radius = weaker attraction between nucleus and outer electron
What is the ionic equation for:
Chlorine + Sodium Bromide -> Bromine + Sodium Chloride
Cl2 + 2Br- -> Br2 + 2Cl-
Observation when Cl2 reacts with Br-
Br2 produced - orange solution
Observation when Cl2 reacts with I-
I2 produced - brown solution (black solid)
Observation when Br2 reacts with I-
I2 produced - brown solution (black solid)
Why is chlorine added to water?
Sterilises water by killing bacteria
Why must chlorine be added in low concentrations?
It is toxic
What is the reaction between chlorine and water?
H2O + Cl2 <–> HCl + HClO
What is disproportionation?
A reaction in which a substance is simultaneously oxidized and reduced, giving two different products
What is the trend in the reactivity of group 2 metals down the group?
Increases
Equation for a group 2 metal reacting with liquid water
X(s) + H2O(l) -> X(OH)2 + H2(g)
Equation for a group 2 metal reacting with steam
X(s) + H2O(g) -> XO(s) + H2(g)
What are the observations of reaction with group 2 metals and water?
- White solid produced
- Bright white light
Equation for when Mg is used in the extraction of Ti from TiCl4
TiCl4 + 2Mg -> 2MgCl2 + Ti
What agent is Mg during its use in the extraction of Ti
Reducing agent
What is the trend of the solubility of group 2 hydroxides?
Increases down the group
Ionic equation for the formation of Magnesium Hydroxide
Mg2+ + 2OH- -> Mg(OH)2
What is the observation for reaction between Mg and OH-?
White precipitate forms
What can be used to test for the presence of Mg2+ ions in a solution?
NaOH
What can be used to test for the presence of OH- ions in a solution?
Mg(NO3)2
Uses of Magnesium Hydroxide?
- Indigestion relief (neutralises stomach acid)
- Often called “milk of magnesia”
What is the trend in the solubility of group 2 sulphates?
Decreases down the group
Ionic equation for the formation of Barium Sulphate
Ba2+ + SO4 2- -> BaSO4
What can be used to test for the presence of Ba2+ ions in a solution?
H2SO4 or Na2SO4
What is the observation for reaction between Ba and SO4 2-?
Formation of a white precipitate
What can be used to test for the presence of SO4 2- ions in a solution?
Acidified BaCl2
Uses of Barium Sulphate
- Stomach X-rays (barium meal)
What are the dangers of using Ba2+ ions?
They are toxic
Observation with the reaction with carbonate impurities
Effervescence